Concealed-type fire protection sprinklers, which discharge a fire fighting fluid such as a water, gas or other chemical agent, can be designed to protect a variety of occupancies, both commercial and residential. In addition, the concealed-type sprinkler can be mounted in a pendant style configuration from a ceiling system or alternatively, the sprinkler can be configured as a sidewall sprinkler for mounting along a wall surface. Generally, the concealing feature of these sprinklers obscures the internal components from view. Thus, a concealed-type sprinkler is useful in residential occupancies for at least aesthetic reasons. One type of commercial occupancy in which a concealed-type sprinkler is employed is an institutional occupancy which includes, for example, correctional, detention, and mental health care facilities. Concealed-type sprinklers for institutional applications are preferably configured to have a tamper resistant thermally sensitive release mechanism to reduce the opportunity for occupants to injure themselves or others with the internal components of the sprinkler.
Industry accepted design criteria exists to minimize the hazard that concealed-type sprinklers may pose. For example, design criteria provides that an concealed sprinkler should be configured with a thermally sensitive trigger or release mechanism that can break away from the body of the sprinkler when a load of eighty pounds or more is suspended from the mechanism. Such criteria minimizes that the potential for someone to use the sprinkler as a device from which to hang themselves or others. Some known concealed sprinklers use a cover to conceal the internal components of the sprinkler in order to prevent unauthorized tampering with the sprinkler and its components. For example, U.S. Pat. No. 6,152,236 is directed to a combined trigger and concealing device for a sprinkler head to conceal components contained within the interior of the sprinkler body. The body and concealing device are further shown disposed within the recess of an escutcheon. The circular concealing device includes two overlapping fusible plates joined by a fusible bonding material which fails in the presence of a sufficient level of heat. In order to conceal the interior of the sprinkler body and provide a pathway for heat transfer to reach the interior of the concealing device, the concealing device is located a preselected distance below the bottom of the sprinkler body and a preselected radial distance within a boundary of the interior of the body. The concealing device therefore defines an annulus or gap between the device and the sprinkler body which is as much as 1/16 inches wide and ⅛ inch high. The concealing device also acts as a component of a trigger device by maintaining a pair of actuating pins in a biased position to hold an adjustment plate in place for supporting a closure member. The concealing device includes a pair of apertures disposed about a central opening to engage the actuating pins. The central opening provides access to an adjustment screw which applies a sealing pressure on the closure member.
It is believed that in one known sprinkler that uses a pair of actuating pins and a concealing device spaced from the bottom of the sprinkler, the gap between the concealing device and the sprinkler body provides access in which a wire or string can be threaded about the actuating pins to hold their relative positions. With the pins held in place, the concealing device can be removed without actuating the sprinkler thereby providing unauthorized access to the internal components of the sprinkler. Other known sprinklers having a cover engaged with a component internal to the sprinkler body in order to conceal the body interior of the sprinkler body are shown and described in U.S. Pat. Nos. 3,783,947, 6,520,865, and 6,367,559. Each of the these patents describe a cover or fusible plate assembly for a sprinkler body that includes a central opening for a tool or other object to access the interior of the body and adjust an internal component. In addition, each of the covers are shown as being within the perimeter of the interior of the sprinkler body and flush with or below the opening at the bottom of the sprinkler body.
Another concealed sprinkler is shown and described in U.S. Pat. No. 4,596,289 in which a cover member and valve closure means completely conceals the interior of the sprinkler body. However, the cover device is not completely supported in place by the sprinkler body or its internal components but instead engages a separate housing surrounding the body to support the outer tabs or projections of the cover.